The present application is a 371 of PCT/JP00/01983, which was filed on Mar. 29th 2000, which claims the benefit of Japanese Patent Application No. 11-88500, filed Aug. 30th 1999.
The present invention relates to a method and apparatus for mounting electronic components such as a microchip or a semiconductor element onto a substrate. More particularly, the invention relates to a component mounting method and apparatus which employs a suction nozzle for holding and mounting a component onto a given area on a substrate.
In a conventional electronic component mounting apparatus, the speed of the mounting operation has been increased by raising the operating speed of the various drive units in order to cope with a demand for high-speed component mounting due to an increase in the number of components to be mounted. For example, in a component mounting apparatus shown in diagrammatic plan view in FIG. 6, a component supply table 2 on which a plurality of component supply units 1 are arranged is moved in the direction of arrangement of the component supply units 1, so as to locate a component supply port 3 of a desired component supply unit 1 in position at a first station ST1 for picking up components (not shown). A component supply unit 1, known as a parts cassette, includes a holding tape (not shown) having recesses for storing electronic components, the recesses being arranged at intervals in the length direction of the holding tape, and a cover tape (not shown) stuck onto the upper surface of the holding tape, the cover tape used for preventing the electronic components from falling out, thereby supplying the components to the component supply port 3 continuously.
The component mounting apparatus also includes a rotary-type mounting head 9. The mounting head 9 includes a rotary drum 8 having a plurality of nozzle units (not shown) equipped with a suction nozzle 7 (ten are shown by way of example in the Figure) at their bottom ends, the nozzle units arranged at equal intervals on the periphery of the drum 8.
The components are mounted onto a substrate 10 by the following procedure: the rotary drum 8 is intermittently rotated through an angle corresponding to the interval of the nozzle units, whereby the suction nozzles 7 of the nozzle units are successively positioned at first to tenth stations ST1 to ST10. By vertical movement of the nozzle unit, the suction nozzle 7 positioned at the first station ST1 picks up an electronic component from a component supply port 3 of a component supply unit 1. When the component held by the suction nozzle 7 is transported with the rotation of the rotary drum 8 and the nozzle 7 is positioned at a third station ST3 for component recognition, the amount of positional offset of the component with respect to the center of the suction nozzle 7 and the position of the component itself are measured using image data picked up by a recognition camera (not shown) of a component recognition device 11. Then, when the component reaches a fifth station ST5 for position correction, the component is rotated by the nozzle unit by the amount of the offset in order to correct the offset of the component calculated by the image processing described above.
When the component is positioned in and stopped at a sixth station ST6 for component mounting, a substrate 10 is located by moving a substrate holding table 12 in X and Y directions so that a desired component mounting area of the substrate 10 is positioned directly below the component held by the suction nozzle 7. Then, the nozzle unit moves vertically, whereby the component held by the suction nozzle 7 is mounted onto the desired mounting area on the substrate 10. In the seventh to tenth stations ST7 to ST10, preparation for next component mounting such as replacement of the suction nozzle 7 is performed.
As typified by cellular phones, recent reduction in weight and thickness of electronic devices necessitates miniaturization of the substrate 10 which is accommodated therein, as well as mounting of smaller components with high density on the substrate. However, reduction of separation of adjacent components is limited by the mechanical structure of the electronic component mounting apparatus. The mounting precision of the electronic component mounting apparatus is scarcely a factor in restricting the reduction of separation of the components, since they are mounted on the substrate 10 after their position has been corrected in the fifth station ST5 in accordance with the correction values calculated from the image data picked up at the third station ST3.
FIG. 7 is a diagrammatical recognition screen 13 which is picked up by the recognition camera of the component recognition device 11 at the third station ST3. Using this recognition screen 13, the amount of offset (xcex94x, xcex94y) of the positional coordinates (x1, y1) of the center 17a of the image 17 of the component held by the suction nozzle 7 with respect to the positional coordinates (x, y) of the center 14a of the image 14 of the suction nozzle 7, and the inclination of the electronic component with respect to the suction nozzle 7 are calculated. A correction value is calculated based on the data, and the position of the component is corrected in accordance with the correction value before it is mounted on the substrate 10. Due to the improvement in resolution of the component recognition device, there is no particular problem in reducing the mounting separation of the components.
However, regarding the mechanical structure of the electronic component mounting apparatus, there is a problem as shown in FIG. 8. When the nozzle unit 19 holding a component 18 with a suction nozzle 7, the component 18 being in a positionally offset condition and corrected to face a given component mounting area of the substrate 10, is lowered, the suction nozzle 7 may come into contact with a component 18 that has already been mounted in an adjacent position as shown at portion A, thereby damaging this component 18 and impairing the quality of the substrate 10.
In order to avoid the problem, a suction nozzle 7 may have an extremely minute shape that it does not contact a previously mounted component 18. However, the smaller the aperture of the suction nozzle 7 becomes, the lower the suctional force on a component 18 is, causing an increase in the rate of failure in picking up a component 18, as well as an increase in the number of components 18 that are discarded due to the failure, and consequent economic loss. What is worse, the strength of the suction nozzle 7 is lowered due to increasing thinness of its outer wall, resulting in an increased frequency of maintenance of the suction nozzle 7 and increased costs.
The invention has been devised in the light of the above problems, and it is an object of the invention to provide a method and apparatus for mounting electronic components realizing the mounting of components at high densities on substrates employing a conventional suction nozzle without lowering the quality of the substrate due to damage of the components.
To achieve the above object, a component mounting method according to the present invention includes the following steps: an electronic with a suction nozzle and transported to above a substrate; the amount of offset of the component with respect to the suction nozzle is calculated; the feasibility of mounting the component held by the suction nozzle onto the substrate without hindrance is determined based on the amount of offset; and a component in respect of which the result of the determination is positive is mounted on the substrate.
According to the component mounting method, high quality of the substrates is achieved since the component held by the suction nozzle is arranged to be mounted on the substrate only when the amount of offset of the component is of such a degree that the suction nozzle face the substrate without hindrance during the mounting operation.
Preferably, the feasibility of mounting the component held by the suction nozzle on the substrate without hindrance is determined as follows: a range of the substrate, the range being faced by the suction nozzle when a component held by the suction nozzle is mounted is determined from the amount of offset of the component; whether or not the range overlaps an electronic component that is already mounted adjacent to the position where the component held by the suction nozzle is to be mounted is judged; and a component in respect of which the result of the judgment is positive is mounted on the substrate.
Accordingly, when it is judged that if a component held by the suction nozzle were to be mounted the suction nozzle would come into contact with an already-mounted component, mounting of this component is not carried out. The damage which would be caused by contact of the suction nozzle with an already-mounted component is thus prevented, enabling substrates to have high quality.
It is also preferred that if it is judged that the range of the substrate would overlap with an electronic component already mounted, and the component currently held by the suction nozzle does not have polarity, a range of the substrate that would be faced by the suction nozzle if the component currently held by the suction nozzle were mounted on the substrate is calculated from the amount of offset that the component would have if it were rotated through 180xc2x0; the feasibility of mounting the component held by the suction nozzle onto the substrate without hindrance is determined in accordance with whether or not there would be overlap of the range of the substrate with the component already mounted adjacent to the position where the component currently held by the suction nozzle is to be mounted; and a component in respect of which the result of this determination is positive is rotated through 180xc2x0 and then is mounted on the substrate.
Thereby, in addition to preventing damage caused by the suction nozzle coming into contact with an already-mounted component, the number of discarded components is greatly reduced since in cases where it is found that contact of the suction nozzle with an adjacent already-mounted component can be avoided if a component that does not have polarity is reversed, mounting is performed after rotating the component through 180xc2x0, thereby reducing the costs.
Furthermore, according to the invention, the feasibility of mounting the component currently held by the suction nozzle on the substrate without hindrance may be determined in accordance with whether or not the offset of the component with respect to the suction nozzle is smaller a pre-set value, and a component in respect of which the result of the determination is positive is mounted on the substrate.
The component mounting method of the invention has advantages in that damage caused by contact of a suction nozzle with an already-mounted component is prevented, thereby ensuring high quality of a substrate and the control processing of mounting is simplified.
An electronic component mounting apparatus according to the present invention includes a mounting head which picks up an electronic component supplied from a component supply unit using a suction nozzle, and transports and mounts the component onto a substrate; an offset amount calculating device which calculates the amount of offset of the component with respect to the suction nozzle by image recognition of the component during the process of transporting the component; and a feasibility determining device which determines the feasibility of mounting the component currently held by the suction nozzle on the substrate without hindrance based on the amount of offset; wherein the component is mounted onto the substrate if the result of the determination by the feasibility determining device is positive.
The electronic component mounting apparatus realizes the component mounting method of the invention and achieves the benefits of the component mounting method due to the provision of the feasibility determining device which determines the feasibility of mounting the component held by the suction nozzle onto the substrate without hindrance based on the amount of offset of the component with respect to the suction nozzle. Further, the apparatus is inexpensive since the feasibility of mounting is determined based on the amount of offset of the component calculated by the component recognition device employed in the conventional electronic component mounting apparatus.